A nonaqueous secondary battery such as a lithium secondary battery has already been put to practical use as a source of electric energy for portable telephones, notebook computers and the like, and additionally has attempted to be applied in medium- and large-sized uses such as automobile use and electric power storage use.
A nonaqueous secondary battery has been demanded, which offers a small decrease in electric capacity in the case of repeating charge and discharge, that is, excellent cyclability. Also, a lithium secondary battery has large electric capacity though it is small in size, so that it has been demanded that safety in the case of exterior short circuit and interior short circuit be improved; a method for producing an active material has been demanded, which allows such a nonaqueous secondary battery excellent in cyclability and high in safety.
Then, a method for producing a positive electrode active material for a nonaqueous secondary battery has been proposed, such that the surface of lithium-containing complex oxide containing nickel is subject to a coating treatment with a compound having any of Mg, Si, Ti, Al, V, Co, K, Ca, Na and B (for example, Japanese Unexamined Patent Publication No. 2001-28265). However, a nonaqueous secondary battery produced by using the obtained positive electrode active material for a nonaqueous secondary battery is insufficient in cyclability as well as safety.